The invention relates to hydraulic systems, including hydraulic drive systems for operating hydraulically driven machinery and equipment. More specifically, the invention relates to an operate check valve that can be interposed between a hydraulic pump operable to pump hydraulic oil in both normal and reverse directions and a hydraulic actuator that is driven by this hydraulic oil. The invention relates further to a hydraulic driving unit that includes the hydraulic pump, the hydraulic actuator, the operate check valve and a tank for storing the hydraulic oil, in which the hydraulic driving unit generates and imparts a hydraulic driving force to a driven body.
Hydraulic drive units for generating a driving force through oil pressure have been used, for example, as lift mechanisms for operating work elements of agricultural and ground cultivating vehicles. Hydraulic drive units of this type are convenient in that they can serve as drive units for hydraulically-driven work elements without the need to lay extensive hydraulic pipe, needing only an electric power source to operate. Such units are expected to continue to be important and to see even wider application in the future.
Hydraulic drive units of this general type are described, for example, in Japanese Patent No. 2824659 and Japanese Patent Laid-Open No. 2003-172307.